The present invention relates to storage batteries. More specifically, the present invention relates to a system for counteracting self-discharge in a storage battery.
Chemical batteries which create electricity from chemical reactions have been known for many years. Such batteries are becoming increasingly important and have found uses throughout industry. These uses include automobiles, UPS systems, etc.
One of the most commonly used chemical batteries are lead acid storage batteries. A lead acid battery cell includes positive and negative lead plates of slightly different composition in a dilute sulfuric acid electrolyte. As the cell discharges, sulfur molecules from the electrolyte bond with the lead plates, releasing excess electrons. As the cell charges, excess electrons bond with sulfur compounds forcing the sulfur molecules back into the sulfuric acid solution.
When a lead acid battery is left idle for a substantial period of time without being recharged, a build-up of sulfur molecules on the battery plates takes place due to self-discharge of the battery. This formation of sulfur on the battery plates is called sulfation. Sulfation hardens the battery plates, reducing and eventually destroying the ability of the battery to generate charge. In lead acid batteries employing thin film positive and negative plates, relatively rapid hardening of the plates due to sulfation occurs because the plates are ultra-thin films.
One prior art technique used to counteract self-discharge in lead acid batteries involves connecting an alkaline battery (or multiple series connected alkaline batteries) in parallel with the lead acid battery when it is left idle. The alkaline battery provides a charging voltage that counteracts self-discharge in the lead acid storage battery. However, when a relatively small drop in the capacity of the alkaline battery takes place, the charging voltage drops below the rated voltage of the lead acid storage battery resulting in self-discharge and sulfation in the lead acid battery. Thus, to prevent self-discharge using this technique, alkaline batteries have to be replaced frequently because they are unsuitable even after a small loss of capacity. This technique for preventing self-discharge in lead acid batteries is inconvenient and costly.